‘wpgf‘k—S '- “w'm‘m: ‘r' I ‘ ," 3143' r l J H‘ 1 ‘ ‘I i x r ‘H. I w ,3 I l > ? i x ‘ i , 1 I 1 II N r‘ I \ A. M i. l ‘ l A l :l W J Hi If 7 m l H i TYNE 1,: SAME WAS“ Ci? scmmw ANA} £3 CC» MPG {SHDS :3: ”ME :3?! “I? :‘3R££2?"S?A?i:fi S’hoas’és fa»? fits Sag-ta m’ M 5. 35°34 AN S‘i .A‘i‘E ECEELLEGE EMS Fmderick Dunn @9138 {’4 ‘A;‘_’ . -.’.--V.L‘--'$‘ ‘q‘. ‘ .1. (MFA ‘34., This is to certify that the thesis entitled . . . THE CHEHSTRY 0F SGLNDIUII AND ITS C(MPOUNDS : - I: THE pH 01“ PRECIPITATION OF SCANDIUII HYDROXIDE - . ~ " . .‘I . I presented by .3 Paul Frederick Dunn 1 . j . . ,4 has been accepted towards fulfillment . of the requirements for i ‘ -.—h c...- C Major professor "va‘"? «Page? I " # *—' u - ‘l .v '.:\"’ e .'-\ ‘. 2n ‘ U THE CHEMIS'IRY OF SClNDIUM AND ITS C(MPOUNDS I: THE pH 01'" PRECIPITATION 0F SCANDIUM HYDROXIDE By PAUL FREDERICK DUNN A THESIS Submitted to the School of Graduate Studies of Elohim State College of Agriculture and Applied Science in partial fulfillnent of the requirements ~ for the degree of mm OF SCIENCE Department of Che-ism 19M 7546 peas 5/7/56 1_ umMnmmmw The author wishes to express his gratitude to Professor L. L. Quill, for his considerate and able guidance of this work and to Dr. F. R. Duke, for his assistance in the interpretation of re- sults. 206083 INTRODUCTION Scandiun was discovered in 1879 by L. l". Eileen (1). It was obtained as a n—ber of the yttrium earth group fran gadolini‘te. Eileen (2) and P. T. Cleve (3) did much of the early study of the properties and the ate-1e weight deterninations on scandim. In the years 1908 to 1910 a great volune of work was done by Sir In. Crookes (h, 5, 6) en the preparation and properties of scandim capounds. Its identificatim within the triad Sc..I...La(B.E) and its cuetaary occurrence in earth minerals, has caused the chassis- try of ecandiun to be closely associated with that of the rare earths. The chuieal relationships of scandiua to the rare earths and the inter-relationships within the earths thuselvee has been the subject of a thorough review by lloeller and Kruers (7). Because of the great siailarity of all the Group IIIa elenents, a large portion of the research effort has been directed at finding sue property, ehuical or physical, by Issue of which separations anon; the numbers of the series might be obtained. the custaary methods lake use of slall differences in the solubilitiee of vari- ous salts, such as the double magnesia nitrates, double potassiun carbmatee, double sulfates, and others. The general relationships as to basicity of the n-bers have been studied (8) with the idea of asking partial subdivision of the group possible by means of precipitations at controlled pH's. No general success has been .1- net in this attupt, although a separation of La fr- the other earths is possible. Since direct infornation on the basic properties of scandiun is sueehat incanplete, this work has been concerned with the pH of precipitation of scandim hydrox- ide from solutions of various salts, and the subsequent calcula- tion of solubility and solubility product constants. EXPERIMENTAL 1. Purification of Scandiu The source material used in this study was scandiun oxalate, in which the only inpurity was a enall amount of calcium, esti- nated to be of the order of 3 to h percent. it the outset of this work several methods were used to remove the calcium a) A method which offers opportunity of obtaining naterial of the highest purity (9) depends upon the conversion of scandiu oxide to the chloride by passing (2021.1t vapor over the oxide at 750° to 800° 0. in a quarts apparatus, and sublining at 900° to 950° C. it this tuperature CaClz shows no appreciable vapor pressure, and the scandiun is thus obtained pure. i'his method was not used in this phase of the work because of the canplexity of the apparatus, and it was felt such high order purity was not necessary. b) i nethod was proposed in which a very concentrated solu- tion of scanctim chloride was saturated with dry hydrogen chloride with the hope that anlqdreus scandiun chloride would precipitate, leaving the calcim in solution. The method was not found success- ful. Due to the extreme solubility of the ecandiu chloride with the consequent necessity of [using nall voluaes of solutions, and the high viscosity of such solutions, the saturation with hydrogen chloride is very difficult. The method was considered ilpractical for this work. c) a hotbed has been described by N. a. sum (9) m- the purificatim of scandin which makes use of the fact that scandium, like aluminua, focus a fluoride coupler ScF6m, soluble in mess fluoride ion, whereas calciun fluoride is insoluble. The solu- tion of scandiun salt is poured into an excess of hot moniun fluoride, whereupon the calcim is precipitated and the scandium r-aine in solution. The nethod as used in this study was nodi- fied slightly, since the amount of calciun was low. Scandim oxide was digested with hydrofluoric acid to convert the oxides to fluorides; then the excess Wdrofluoric acid was neutralised with annonia. Sufficient excess mania was added to convert only a portion of the scandiun to the soluble coupler. The solution was decanted and filtered through a platinum funnel. The filtrate was then evaporated with sulfuric acid to reaove all fluorides, then gently ignited to remove amoniun salts. The scandiun samples obtained by this nethod still showed traces of calciun when ennined spectroscopically. The intensi- ties of the calcium lines in the speetrogrsn of the sanplee were approrinately the sane as those frn the blank run on the carbon electrode. The naterial was considered of sufficiently high purity for this work. However, the nethod is involved, and the requiruent of a large anount of platinum were made it inpractical for purifying fairly large amounts of scandiun. d) The method finally adopted for this work involved the re- peated precipitation of scandiun hydroxide free a chloride .5. solution near the boiling temperature. Although calcium hydroxide is less soluble in hot solution than in cold, the ease with which filtration fran hot solution is accanplished is much greater. The scandium oxide was dissolved in kwdro-p chloric acid, heated to boiling, and precipitated with monia. Excess amonia was avoided in order that the solubility product of calcium hydroxide would not be exceeded. The precipitate was filtered through a steam Jacketed funnel, redissolved in Just sufficient hydrochloric acid to effect solution, and the process repeated. It was found that four successive precipita- tions in the manner described gave a product of purity emparable to that obtained frm the fluoride purification. 2. The pH Titration of Scandiun Salts The purified scandium was made into solutions of various salts: chloride, nitrate, and sulfate. When different concen- trations of the same salt were desired, they were obtained by volunetric dilution. Analyses of the solutions were made by precipitation of scandiun oxalate fran slightly acid solutions. Sufficient oxalic acid solution, saturated at about 50°C. , to give apprmnately a fivefold excess was added to the hot sample. After digestion at Just below boiling for two hours, the crystal- line scandiun oxalate was filtered (cold), ignited and weighed. To minimize solubility losses the transfer of the precipitate to the filter was .done with the filtrate itself. The nethod was not entirely satisfactory for, with parallel samples yielding about 50 ng. of Sc203, agreement better than two percent was not -5- obtained. ill. stated concentrations in the following tables are averages of at least two deteninations. In all cases the pH titrations were made an 25 n1. sulples as measured from a burette. The pH was neasured with a Bach-n pH Ester using a glass electrode against a saturated calmel electrode. The sodiun hydroxide used for the titrations was 0.2121; N. The data on scandiun chloride are given in Table I and Figure I; for scandiun nitrate in Table II and III and Figures II, III, V5 for scandiua sulfate in Table IV and Figures IV, V. TABLE I Titration.Data on Scandium.Chloride Note: Scolg 3 0.011114 Molar; 25 :11. sample 3 391$"- noles. The values corresponding to a certain nol ratio 5 +++ -»Q is c given by: v - £255“th (1000) .2135 q = 1.691; 0. - Normality of NaOH = 0.212h. ' Q V 5% No. NaOH (n1.) 1 2 3 h W pH pjfir pi? pH 0.0 0.00 3.35 3.55 3.60 3.30 0.2 0.39 3.57 3.88 3.87 3.7h 0.h 0.68 3.67 h.07 h.02 3.97 0.6 1.02 3.77 h.25 h.25 h.22 0.8 1.36 3.8h h.38 h.38 h.38 1.0 1.69 3.90 ho50 b.50 h.55 1.2 .2.03 3.95 h.6l h.62 h.70 1.h 2.h7 h.00 h.70 h.72 h.88 1.6 2.71 h.76 h.79 h.98 1.8 3.05 h.8h h.8h 5.12 2.0 3.39 h.05 14.88 h.89 5.19 2.2 3.73 h-O’I b.9h 17.98 5.2!: 2.h h.07 h.1h h.98 h.98 5.28 2.5 b.2h h.18 5.01 5.00 5.33 2.6 h.h1 h.2h 5.03 5.02 5.37 2.7 h.58 h.32 5.05 5.08 5.h5 2.8 h.75 h.h2 5.11: 5.18 5.57 2.9 h.91 11.58 5.80 5.14.1 5.75 3.0 5.08 5.10 5.80 5.78 6.h0 3.1 5.26 5.9h 6.25 6.25 7.13 302 Sol-82 6e28 6e7° 6e62 7e58 3.3 5.60 6.52 6.93 6.88 7.90 3.h 5.76 6.70 7.07 7.0h 8.12 3e5 5e9h 6e87 7e22 7e18 8e32 3.6 6.10 7.00 7.32 7.30 8.h5 3.7 6.27 7.08 7.h0 7.38 8.57 3.8 6.h5 7.18 7.50 7.h8 8.67 h.0 6.78 7.30 7.63 7.63 8.83 ho5 7.63 7.57 7.87 7.88 9.13 5.0 8.h7 7.78 8.03 8.05 9.33 5.5 9.33 7.95 8.23 8.23 9.55 6.0 10.17 8.13 8.h1 8.h3 9.73 6e6 11.18 8am 8e68 8.70 10.00 TABLE I (Cont'd) Q V M10 NOe noon (ml.) Sc ‘ 1 2 3 1; W if p? pr— 6.9 11.69 8.63 8.88 8.88 10.18 7.2 12.20 8.92 9.15 9.1h 10.h0 7.h 12.53 9.18 9.80 9.37 10.72 7.6 12.87 9.h6 9.67 9.67 11.03 7.8 13.22 9.69 9.92 9.90 11.28 8.0 13.56 9.85 10.08 10.08 11.h0 8.2 13.90 9.99 10.20 10.23; 11.56 8.h 11.23 10.10 10.32 10.30 11.65 8.6 1h.58 10.18 10.h0 10.38 11.72 8.8 18.91 10.25 .10;E5 10.hs 11.80 9.0 15.2h 10.30 10.50 10.51' 11.85 . TABLE II _ Titration Date on Sc(N03)3 Note: For Sample #5, V . 0.7h Q For Sample #6, #7, v . 1.85 0 Sam ls # 5 6 7 ConcE'ifi-atiea: 1.00628 ll) 0. M . Q 7 pH V pH pH 912324} (n1.) (n1.) SC 'I’ l- 0.0 0.0 3.68 0.0 3.20 3.35 0.2 0.15 3.98 0.37 3.67 3.67 0.h 0.30 h.25 0.7h 3.96 ‘ 3.95 Oe6 Oahu 11.50 1011 ‘ he 17 hols 0.8 0.59 h.70 l.h8 h.35 h.38 1.0 007‘} heal-l 1.85 ’ new 16053 1.2 0.89 h.93 2.22 h.60 h.62 1.1 1.0:. 5.00 2.59 1.068 8.67 1.6 1.18 5.07 2.96 h.78 h.75 1.8 1.33 5.15 3.33 ho90 8.85 2.0 law 5625 3.70 5.02 he96 2.2 1.63 5.37 h.07 5.08 5.08 2.h 1.78 5.52 h.hh 5.33 5.25 2.6 1.92 5.68 h.81 5.53 5.h6 2.8 2.07 6.00 5.18 6.12 6.00 3.0 2.22 7.82 5.55 7.80 7.90 3.2 2.37 10.07 5.92 10.10 10.18 3.h 2.52 10.50 6.29 10.70 10.60 3.6 2.66 10.75 6.66 ‘ 11.00 10.88 3.8 2.81 10.95 7.0h 11.15 11.08 h.0 2.96 11.10 Note: Q NaOH Sc+++ 0.0 0.2 0.1; 0.6 0.8 1.0 1.2 1.h 1.6 1.8 . 2.0 2.2 2.h 2.6 2.8 3.0 3.2 3.h 3.6 3.8 h.0 h.2 h.h h.6 h.8 V (mlo) 0.00 0.78 1.h8 2.22 2.96 3.70 8.88 5.18 5.92 7.80 8.1h 8.88 9.62 10.37 11.10 11.8h 12.59 13.33 1h.07 1h.81 15.55 16.28 17.02 17.77 TABLE III pH 3.27 3.70 h.22 ho37 h.53 8.60 h.78 8.90 5.03 5.28 5.62 6.78 8.85 10.27 10.70 10.90 11.03 11.08 Q HOOK Sc 5.0 5.2 5.h 5.6 5.8 6.0 6.2 6.h 6.6 7.8 W‘O‘O‘O Copacabana-14 PNOQOMP'NOGQ H 0‘0 e e e oooo~ ~10— Titration.Data on Sc(N03)3 V (n1.) 18.51 19.25 20.00 20.72 21.h3 22.20 22.95 23.69 Zh.h2 25.15 25.90 26.65 27.ho 28.12 28.88 29.60 30.33 31.08 31.81 32.55 33.30 3h.05 3h.80 35.50 36.27 37.00 For Sample 8, V = 3.70 Q, Concentration a 0.031h M pH 11.30 11.37 11.h llth 11.55 TABLE IV Titration Dita on 302(50h)3 Concentration :- 0.00753 M; V a 1.77 Q Sanple No.2 9 10 Q 7 pH PH Egg (do) 80"” 0.0 0.0 3.63 3.70 0.1 0.18 h.08 h.12 0.2 0.35 h.28 h.32 0.3 0.53 hth h.h5 0.8 0.71 8.55 h.57 0.5 0.88 h.63 h.63 0.6 1.06 h.70 h.68 00? lezlt h07h h. 73 0.8 l.h2 h.78 h.78 0.9 1.59 h.83 h.82 1.0 1.77 h.87 h.86 1.1 1.95 £2.92 h-89 1.2 2.12 h.96 h.92 1.3 2.30 5.01 ho97 1.h 2.h8 5.05 .00 1.5 2.66 5.10 5.05 1.6 2.83 5.1h 5.08 1.7 3.01 5.18 5.12 1.8 3e19 5023 5017 lo? 3e36 5e28 5.20 2.0 3.51. 5.33 5-23 2a]. 3072 5036 5027 2.2 3.89 5.82 5.31 2e3 I400? 50,65 5035 2.1. 8.25 5.51 5.38 2.5 h.83 5.55 S.h3 2.6 heéo 5060 Sch-8 2.? 8.78 5061! 5053 2e8 16096 5070 058 2.9 5.13 5.80 5.68 3.0 5.32 6e03 5085 3,1 5.h8 6.50 6.15 3.2 5.67 7.03 6.73 3.3 5.8h 7.82 7.12 Bah 6.02 7.75 7oh0 3.5 6.19 8.00 7.65 3.6 6.37 8.20 7.88 3.7 6.55 8.35 3.07 TABLE IV (Cont'd) Sample No. 8 9 10 Q 7 pH pH Neon (111.) 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